Now that is a good one Curt ! I usually just cleaned them out with a wire file brush. Once they dulled up, I tossed them in the scrap heap. I never really thought about re-sharpening them. This trivia question puzzles me greatly. There are so many types of file teeth arrangments, from fine to coarse, single straight pitch, to the same in dual cross cut pitch. I can't even imagine how sharpening them is done. I would love to hear the answer to this one for sure. I feel kind of stupid after near 40 years in the machine trades. Pa

Cotten
There no limit to your depth of knowledge. The answer I was looking for is the Hydrochloric acid dip. You soak them in Hydrochloric acid for 5 minutes then rinse. The acid eats away the thinner metals first and leaves a sharp edge on your teeth. Works on almost all files. It also gets rid of buildup between the teeth. I was looking at some of my files the other day and thinking they needed the "treatment".

Never throw the old ones out. Like Cotten said, they will sharpen right up to a fine knife blade. My wife and I participate in 18th Century Living History, when work allows (not much of that lately), and some of the finest hand-made knives we see are from old files. The only free metal available to the colonies (under the Crown) were scrap saw blades and old files. The made all kinds of knives. It takes a bit of tempering to get the file to be less brittle. Some even temper the sharp edge by cooling with clay. I'm not a metalurgist, or even know how metal changes with tempering. But, files are some of the most useful objects, even after worn out. Remember, I'm a packrat.

Some pretty interesting reclaimation technics !! Tossing them in the scrap isn't throwing them out fellas. It is called recycling them. They manage to return as something else sooner or later. I made some spear heads from a few years ago. As Jack said though.......the metal is brittle. Definately got to soften them a bit up for those. Use of the corrosives is real interesting. I have a few favorite files that I wouldn't mind preserving. Like the pool cue chock idea a s well. Aluminum loads a file up quickly. Before you know it, you tear up the surface of the aluminum you are working because of the rapid build up. Anyone know how they sharpen new files ? Pa

I'll never forget the ass chewin I got from my grandad 40 years ago when he caught me using a file and holding it with my bare hands. The salt from your sweat can cause them to rust and he was an old railroad man. He got the point across that you should always be wearing leather gloves when using a file. Jerry

Thanks for the tips guys, I like the chalk one, as it seems the file always loads up and scratches just when I'm getting a nice finish. I'm always on the lookout for files at yard sales, just my opinion, but they don't seem to make them like they used to.
Dr. scrounging Dick